1. Field of the Invention
The present invention relates to water-soluble cyclodextrin derivatives with lipophilic substituents and processes for their preparation.
Water-solubility in the context of the present invention is to be understood as meaning that the product is dissolved in water to the extent of at least 10% by weight at 20.degree. C.
2. The Prior Art
Increasing the water-solubility of cyclodextrin derivatives and cyclodextrin complexes by introduction of hydroxyalkyl, dihydroxyalkyl or carboxymethyl groups is known in the prior art and is used, for example, on active compound complexes in the pharmaceutical sector. Mixed ethers with short-chain hydrophilic substituents show the same result.
J. Pitha, L. Szabo and H. M. Fales, Carbohydr. Res. 1987, 168, 191 describe the reaction of cyclodextrins with propene oxide or 3-hydroxypropene oxide in an aqueous base. This leads to very readily water-soluble derivatives with a relatively sharp and symmetric distribution of substituents.
WO 9200331 describes the preparation of hydroxyalkylated cyclodextrin derivatives by reaction of cyclodextrin with lower epoxides and further reaction thereof to give amino derivatives.
EP 499322 A1 describes the preparation and potential use of hydroxyalkylated cyclodextrin derivatives which contain additional carboxyalkyl groups.
EP 146841 A2 describes the preparation of water-soluble mixed ethers of .beta.-cyclodextrin by reaction with lower epoxides (C1-C4).
The surface-active properties of the water-soluble cyclodextrin derivatives known to date are low in comparison with customary surfactants.
The use of water-soluble cyclodextrins and cyclodextrin derivatives in detergent solutions is made difficult by complexing of the surface-active substances, and is possible to only a limited extent. A number of surface-active cyclodextrin derivatives are described in the literature, methyl or hydroxypropyl substituents on the cyclodextrin already showing influences on the surface-active properties of the derivatives.
U. R. Dharmawardana, S. D. Christian, E. E. Tucker, R. W. Taylor and J. F. Scamehorn, Langmuir 1993, 9, 2258 report that cyclodextrins and cyclodextrin derivatives increase the surface tension and the critical micelle concentration of detergent solutions by formation of inclusion complexes with the detergents.
T. Cserhati and J. Szejtli, Tenside Deterg., 1985, 22, 237 report that methylated .beta.-cyclodextrins have a detectable surface activity and lead to a reduction in surface tension in aqueous solution.
F. M. Menger and D. Y. Williams, Tetrahedron Lett. 1986, 27, 2579 disclose that water-insoluble cyclodextrin derivatives with longer-chain alkyl substituents display surface activity without the occurrence of a critical micelle concentration.
Cyclodextrin derivatives which are substituted by lipophilic substituents and have potent surface-active properties as a rule have a water-solubility of only significantly less than 10%.
DE 4,035,378 (corresponding to CA 117:113485) describes the possibility of finishing textile materials by treatment with cyclodextrin derivatives. To fix cyclodextrin to hydrophobic materials, anchor groups, such as longer-chain alkyl radicals, aryl radicals or alkylaryl radicals, which effect chiefly physical bonding via van der Waals' interactions, are proposed.
For technical and financial reasons (textile finishing processes are as a rule carried out in an aqueous medium), the cyclodextrin derivatives with extensive hydrophobic anchors which are proposed for finishing fabric and fibers of hydrophobic materials should have an adequate water-solubility so that auxiliaries (for example dispersing agents and the like) can largely be omitted.
Cyclodextrin derivatives which have a high surface activity could render the use of these auxiliaries completely superfluous.